Yamunacharya, aka Alavandar, is the earliest Sri Vaishnava Acharya whose philosophical works survive.  He lived in the 10th century, he was Ramanujacharya’s guru’s guru, and he was the grandson of Nathamuni, another Sri Vaishnava Acharya who compiled the Alwars’ poems.  He spent a large part of his life as a king, before being reformed and returning to his Sri Vaishnava heritage.  And he was responsible for bringing Ramanujacharya into the Sri Vaishnava fold.  In any case, this is a compilation of all the surviving works of Yamunacharya:

1.  Agama Pramanya - This is a work defending the authority of the Pancharatra Agamas, a set of scriptures important to Vaishnavism in general and Sri Vaishnavism in particular.  Ramanujacharya borrows arguments from this in defending the Pancharatra Agamas in the Sri Bhashya.

2.  Siddhi Traya - This is a set of three philosophical works explaining the nature of the supreme Lord Vishnu, the nature of the soul, and the nature of knowledge, respectively.  This is the earliest Sri Vaishnava wok on the philosophy of Visistadvaita.

3.  Gitartha Sangraha - This is a 32-verse summary of the Bhagavad Gita.  Ramanujacharya used this as a guide in writing his Bhagavad Gita Bhashya.

4.  Stotra Ratna - This is a 62-verse hymn to Vishnu written in the spirit of Sharanagati or complete surrender to the lotus feet of Vishnu as a means of attaining Moksha.  It was hearing this poem that inspired Ramanujacharya to become a Sri Vaishnava.

5.  Chatussloki - This is a four-verse hymn to the goddess Lakshmi, who serves as mediator between her husband Vishnu and the Jivatmas or individual souls.

There are also some lost works of Yamunacharya - the Purusha Nirnaya, a work establishing the supremacy of Vishnu, and the Kashmira Agama Pramanya, discussing a lost branch of the Vedas on which the Pancharatra Agamas are based.

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